…appear dozens of eager, colourful Mexican families, chattering, clambering and sprawling over the nearest pyramid. It’s quite a shock, given the enormous scale of this citadel high up from the valley floor, to suddenly come across such a packed group colonising a single spot. Where did they come from?

The first thing that strikes you when entering the citadel is the sheer scale of the site, vast planes of open land are characterised and bordered by several hundred artificial terraces with a monumental Observatory in the centre (set at an astronomically calculated angle to the orientation of the rest of the site) and dozens of ziggurat pyramids dotted around the perimeter, some climbable whilst others roped off as the site is still only partially excavated. Its wonderous elevated position makes you feel like you’re on an island in the sky with the hazy valley floor below.